南秦岭勉县-略阳缝合带印支期光头山埃达克质花岗岩的成因及其地质意义  

Genesis of the Indosinian Guangtoushan adakitic biotite plagiogranite in the Mianxian-Lueyang (Mianlue) suture, South Qinling, China, and its tectonic implications

作　　者：秦江锋[1] 赖绍聪[1] 李永飞[1] 

机构地区：[1]西北大学大陆动力学国家重点实验室,西北大学地质学系,陕西西安710069

出　　处：《地质通报》2007年第4期466-471,共6页Geological Bulletin of China

基　　金：国家自然科学基金重点项目(批准号:40234041);高等学校优秀青年教师教学科研奖励计划(教人司[2002]383号)

摘　　要：勉略缝合带北侧的印支期光头山黑云母斜长花岗岩的地球化学研究表明,该套岩石的SiO2≥56%,Al2O3>15%,Na2O>K2O,富集LILE和LREE,负Eu异常不明显,强烈富集Sr(Sr=704.61～1052.81μg/g,平均为828.45μg/g)和亏损Y(Y=7.17～9.68μg/g,平均为7.66μg/g),高Sr/Y比值(80.74～281.41),表现出明显的埃达克岩的地球化学性质。结合岩体产出的时空位置,认为光头山岩体形成于典型的后碰撞构造环境,可能是三叠纪华北和扬子两大板块的碰撞作用导致俯冲板片断离、软流圈物质上涌底侵、下地壳增厚并熔融,产生了具有埃达克性质的熔体和含石榴子石的残余相。Geochemical study of the Indosinian Guangtoushan adakitic biotite plagiogranite at the northern side of the Mianlue suture zone indicates that the rocks are characterized by SiO2≥56%, Al2O3〉15% and Na2O〉K2O, enrichment in LILE and LREE, an unpronounced negative Eu anomaly, strong enrichment in Sr （Sr=704.61-1052.81 μg/g with an average of 828.45 μg/g） and depletion in Y （Y=7.17-9.68 μg/g with an average of 7.66 μg/g） and high Sr/Y ratios （80.74-281.41）, exhibiting the marked geochemical properties of adakite. According to those properties, combined with the temporal-spatial location of occurrence of the intrusion, it is thought that the Guangtoushan intrusion formed in a typical post-collisional tectonic environment. It is possible that the collision between the North China and Yangtze plates during the Triassic resulted in break-off of the subducting slab, upwelling and underplating of asthenospheric materials and thickening and fusion of the lower crust, thus generating melts of adakitic affinity and garnet-bearing residual phases.

关 键 词：南秦岭先头山岩体 黑云母斜长花岗岩 埃达克岩 岩石成因 后碰撞期 

分 类 号：P588.121[天文地球—岩石学] P581[天文地球—地质学]